Wireless communication device

Abstract

To accurately detect a moving direction of a mobile object without increasing a facility cost.SOLUTION: A wireless communication device 10 holds a radiation direction of a transmission beam transmitted by the wireless communication device 10 so that a radio wave intensity detected by a mobile object 20 becomes a direction P deviated from a reference direction N indicating a peak value to either the right or left along a horizontal plane, and detects a moving direction of the mobile object 20 based on the increase or decrease in the radio wave intensity detected by the mobile object 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a moving direction detection technique for detecting the moving direction of a moving object based on the radio wave intensity of a wireless signal transmitted from a wireless communication device, detected by the moving object. [Background technology]

[0002] In recent years, wireless systems have been used that perform wireless communication with mobile objects with high gain by controlling the radiation direction and shape of a transmission beam through beamforming using multiple antenna elements.Conventionally, in such wireless systems, Patent Document 1 proposes a synchronization signal transmission technology for transmitting a synchronization signal from a wireless communication device to mobile objects within a communication range, in which a transmission beam with a narrow beam width is emitted sequentially while being shifted little by little along a horizontal plane. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6336728 Summary of the Invention [Problem to be solved by the invention]

[0004] According to such conventional technology, the radio wave intensity detected by a moving object is highest when the moving object is located at the center of the transmission beam, and tends to decrease as the moving object moves away from the center of the transmission beam toward the periphery. Therefore, by utilizing the relationship between the position of a moving object within such a transmission beam and the radio wave intensity detected by the moving object, the position of the moving object within the transmission beam can be detected in detail. For example, if a wireless communication device maintains the radiation direction of the transmission beam in the direction in which the radio wave strength notified from the mobile body is at its peak, i.e., the direction in which the mobile body is located at the center of the transmission beam, then if the radio wave strength of the mobile body subsequently decreases, the wireless communication device can detect that the mobile body has moved in a direction away from the center within the transmission beam.

[0005] With this configuration, it is possible to estimate that a moving object has moved away from the center of the transmission beam toward the periphery, but it is not possible to determine whether the object moved to the left or right of the center of the transmission beam. To address this issue, if multiple wireless communication devices installed in different locations capture the same moving object at the center of the transmission beam, the direction of movement can be accurately detected based on the radio wave intensity reported from the same moving object. Another possible solution is to use a location sensor such as a GPS mounted on the moving object. However, with such a technology for detecting the direction of a moving object, in order to accurately detect the direction of the moving object, it is necessary to prepare multiple pieces of hardware, such as wireless communication devices and position sensors, in the existing wireless system, which poses the problem of increased equipment costs.

[0006] The present invention has been made to solve such problems, and has an object to provide a movement direction detection technique that can accurately detect the movement direction of a moving object without increasing equipment costs. [Means for solving the problem]

[0007] In order to achieve this object, the wireless communication device of the present invention is a wireless communication device comprising a wireless I / F configured to perform wireless communication with a mobile body by transmitting and receiving wireless signals, and a control circuit configured to detect the movement direction of the mobile body based on the radio wave intensity of the radio signal transmitted from the wireless I / F detected by the mobile body, wherein the control circuit is configured to, at the start of detection of the movement direction of the mobile body, maintain the radiation direction of the transmission beam transmitted from the wireless communication device so that it is shifted to either the left or right from the direction in which the radio wave intensity shows a peak value, and to detect the movement direction of the mobile body based on the increase or decrease in the radio wave intensity after the start of detection.

[0008] In addition, in one configuration example of the above-mentioned wireless communication device according to the present invention, the control circuit is configured to change the radio wave intensity of the transmission beam transmitted from the wireless communication device, and to detect the direction of movement of the moving body based on the magnitude of the change in radio wave intensity detected by the moving body relative to the change in radio wave intensity of the transmission beam. [Effects of the Invention]

[0009] According to the present invention, the moving direction of a moving object can be accurately detected without increasing the equipment cost. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing the configuration of a wireless communication device according to this embodiment. [Figure 2] FIG. 2 is a flowchart showing the operation of the wireless communication device according to this embodiment. [Figure 3] FIG. 3 is a diagram illustrating the operation of the wireless communication device according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, an embodiment of the present invention will be described with reference to the drawings. [Wireless communication device] First, a wireless communication device 10 according to the present embodiment will be described with reference to the block diagram of FIG. This wireless communication device 10 is a general wireless communication device such as a base station or master station used in a wireless system, which performs wireless communication with a mobile object 20 by transmitting and receiving wireless signals, and is configured to control the radiation direction and shape of the transmitted beam by beamforming using multiple antenna elements.

[0012] [Principle of the present invention] The transmission beam has a certain beam width, and as the mobile object moves within the transmission beam in a direction away from the beam center (central axis) to the periphery, the radio wave intensity detected by the mobile object gradually decreases. Furthermore, since the transmission beam is formed symmetrically along the horizontal plane from the beam center as viewed from wireless communication device 10, the radio wave intensity also decreases symmetrically. Therefore, if the mobile object is located at the beam center, the radio wave intensity attenuates whether the mobile object moves left or right along the horizontal plane from that position, making it impossible to detect whether the mobile object has moved left or right.

[0013] If a moving object is located away from the center of the beam, the radio wave strength detected by the moving object will gradually decrease as it moves further away from the center of the beam. However, as it moves from that position toward the center of the beam, the radio wave strength detected by the moving object will gradually increase. Therefore, if a moving object is located away from the center of the beam, the increase or decrease in radio wave strength will differ depending on whether it moves left or right from that position, making it possible to detect whether the moving object has moved left or right.

[0014] The present invention focuses on the relationship between the distribution of radio wave strength within such a transmission beam and the position of the moving body, and controls and maintains the radiation direction of the transmission beam so that the detection start direction is shifted to either the left or right along the horizontal plane from the direction in which the radio wave strength shows its peak value, and is configured to detect the direction of movement of the moving body based on the increase or decrease in radio wave strength after the start of movement. As a result, if the radio wave intensity detected by the moving body increases from the start of detection, it can be detected that the moving body has moved toward the center of the beam, and if the radio wave intensity detected by the moving body decreases, it can be detected that the moving body has moved away from the center of the beam.

[0015] In reality, the moving body 20 moves three-dimensionally, but in the present invention, the moving body 20 moves along a horizontal plane, and the direction of movement of the moving body 20 that can be detected in the present invention is the left-right direction (direction away from the central axis) that is perpendicular to the central axis direction of the transmission beam emitted along the horizontal plane. If the distance between the wireless communication device 10 and the moving body 20 changes, the radio wave intensity detected by the moving body 20 also changes, but since the distance can be detected by, for example, the difference in reception time of a radio signal used in Wi-Fi positioning technology, when detecting the movement of the moving body 20 based on the radio wave intensity, the change in radio wave intensity due to distance can also be taken into consideration.

[0016] Furthermore, since the greater the distance between the wireless communication device 10 and the moving body 20, the greater the fluctuation in radio wave intensity when the distance between the wireless communication device 10 and the moving body 20 changes, this can be utilized to change the radio wave intensity of the transmission beam emitted from the wireless communication device 10, and detect the change in the distance between the wireless communication device 10 and the moving body 20 based on the change in radio wave intensity detected at the moving body 20 in that case. When the amount of change in the radio wave intensity detected at the moving body 20 is greater than the amount of change in the radio wave intensity of the transmission beam emitted from the wireless communication device 10, it can be determined that the distance between the wireless communication device 10 and the moving body 20 has increased, and conversely, when the amount of change in the radio wave intensity detected at the moving body 20 is small, it can be determined that the distance between the wireless communication device 10 and the moving body 20 has decreased.

[0017] [Wireless communication device details] Next, with reference to the block diagram of FIG. 1, the configuration of the wireless communication device according to this embodiment will be described in detail. The wireless communication device 10 includes a wireless I / F 11, a memory circuit 12, and a control circuit 13 as its main components.

[0018] [Wireless I / F] The wireless I / F 11 performs wireless communication with the mobile body 20 by transmitting and receiving wireless signals, and is configured to adjust the radiation direction and shape of the transmitted beam by beamforming using multiple antenna elements based on the control of the control circuit 13 when transmitting the wireless signal. [Memory circuit] The memory circuit 12 is made up of a storage device such as a semiconductor memory, and is configured to store various processing data and programs used in the process of detecting the moving direction of the moving object 20 executed by the control circuit. This program is read out in advance from an external device or a recording medium (neither of which is shown) and stored in the memory circuit 12. The main processing data stored in the memory circuit 12 includes an offset value Δ for specifying the detection start direction of the transmitted beam.

[0019] [Control circuit] The control circuit 13 has a CPU and its peripheral circuits, and is configured to read a program stored in the memory circuit 12 and operate in cooperation with the CPU to execute a process for detecting the direction of movement of the moving body 20 based on the processing data of the memory circuit 12. That is, at the start of detection, the control circuit 13 controls and maintains the radiation direction of the transmission beam emitted from the wireless I / F 11 toward the moving body 20 based on the offset value Δ stored in the memory circuit 12 so that the detection start direction is shifted to either the left or right from the direction in which the radio wave strength detected at the moving body 20 shows its peak value, and is configured to detect the moving direction of the moving body 20 based on the increase or decrease in the radio wave strength detected at the moving body 20 after this start of detection.

[0020] The radio wave intensity detected by the mobile object 20 may be transmitted to the wireless communication device 10 autonomously by the mobile object 20, or may be transmitted to the wireless communication device 10 by the mobile object 20 in response to a request from the wireless communication device 10. The wireless communication device 10 may refer to information on the radio wave intensity recorded in the mobile object 20.

[0021] [Operation of this embodiment] Next, the operation of the wireless communication device 10 according to the present embodiment will be described with reference to the flowchart of FIG. 2 and the explanatory diagram of FIG. At the start of detection, the control circuit 13 controls the wireless I / F 11 to scan the radiation direction of the transmission beam emitted toward the mobile object 20 from side to side along the horizontal plane, and identifies the direction in which the radio wave intensity acquired from the mobile object 20 shows a peak value, i.e., the direction in which the mobile object 20 is at the center of the transmission beam, as the reference direction N (step 100), as shown in Fig. 3(a). The radio wave intensity in this state, i.e., the peak value, is defined as radio wave intensity Rn.

[0022] Next, the control circuit 13 identifies the detection start direction P based on the offset value Δ in the memory circuit 12 and the reference direction N (step 101), and controls the radiation direction of the transmission beam to the detection start direction P via the wireless I / F 11 (step 102), as shown in Fig. 3(b), and acquires the radio wave intensity Rp at the time of detection start from the moving object 20 (step 103). In this example, the detection start direction P is set to a direction shifted (offset) to the left along the horizontal plane from the center of the beam. In this case, the offset value Δ, i.e., the relationship between the reference direction N and the detection start direction P, can be expressed in terms of radio wave strength. For example, when radio wave strength is used, the offset value Δ is expressed as Rn-Rp, and the direction in which the radio wave strength drops by Δ from Rn can be identified as the detection start direction P.

[0023] Generally, the beam width, which affects the size of the communication area, is defined as the angular width (beam half-angle) where the antenna gain at the beam center is reduced by 3 dB, i.e., halved. Therefore, if Δ=1.5 dB, then the direction shifted to the left or right along the horizontal plane by half the beam width from the reference direction N can be identified as the detection start direction P. Note that the offset value Δ may use values ​​such as the angular width or radio wave intensity ratio instead of radio wave intensity. The offset value Δ depends on various parameters such as the beam width of the transmitted beam, the angular distance of movement of the moving body 20 required to detect the direction of movement, and the distance between the wireless communication device 10 and the moving body 20, and therefore may be set in advance depending on the detection performance required in the application to which the present invention is applied.

[0024] After that, the control circuit 13 waits until a predetermined standby time elapses in consideration of the time required for the movement of the moving body 20 (step 104: NO), and acquires a new radio wave intensity Rq from the moving body 20 after the movement in response to the elapse of the standby time (step 104: YES) (step 105). Subsequently, the control circuit 13 compares the radio wave intensity Rp at the detection start time with the new radio wave intensity Rq, and identifies the moving direction of the moving body 20 based on the increase or decrease thereof (step 106).

[0025] Therefore, as shown in FIG. 3(c), when the radio wave intensity detected by the moving body 20 decreases from the detection start time and Rp > Rq, it is identified that the moving body 20 has moved in a direction away from the beam center. On the other hand, as shown in FIG. 3(d), when the radio wave intensity detected by the moving body 20 increases from the detection start time and Rp < Rq, it is identified that the moving body 20 has moved in a direction approaching the beam center.

[0026] After that, the control circuit 13 waits until the next detection timing arrives (step 107: NO), and returns to step 100 described above in response to the arrival of the detection timing (step 107: YES), identifies a new reference direction N' (step 100), and identifies a new detection start direction P' (step 101).

[0027] Therefore, when the moving body 20 moves in a direction away from the beam center, as shown in FIG. 3(e), the new reference direction N' moves to the right of the immediately preceding reference direction N by the amount that the moving body 20 has moved, and accordingly, the new detection start direction P' also moves to the right. On the other hand, when the moving body 20 moves in a direction approaching the beam center, as shown in FIG. 3(f), the new reference direction N' moves to the left of the immediately preceding reference direction N by the amount that the moving body 20 has moved, and accordingly, the new detection start direction P' also moves to the left.

[0028] [Effects of the Present Embodiment]<00ZZ133>In this way, in the wireless communication device 10, the radiation direction of the transmission beam is controlled and maintained to be a detection start direction P that is shifted to either the left or right along the horizontal plane from the reference direction N where the radio wave intensity detected by the moving body 20 shows its peak value, and the moving direction of the moving body 20 is detected based on the increase or decrease in the radio wave intensity after the start of this movement. Therefore, according to the present invention, there is no need to add hardware such as multiple wireless communication devices or position sensors to an existing wireless system, making it possible to accurately detect the direction of movement of the moving body 20 while avoiding an increase in equipment costs.

[0029] [Extended embodiment] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. [Explanation of symbols]

[0030] 10...wireless communication device, 11...wireless I / F, 12...memory circuit, 13...control circuit, 20...moving body, Δ...offset value, N, N'...reference direction, P, P'...detection start direction, Rn, Rp, Rq...radio wave intensity.

Claims

1. A wireless communication device comprising: a wireless I / F configured to perform wireless communication with a mobile object by transmitting and receiving a wireless signal; and a control circuit configured to detect a moving direction of the mobile object based on a radio wave intensity of the wireless signal transmitted from the wireless I / F, the radio wave intensity being detected by the mobile object; The control circuit At the start of detection of the moving direction of the moving body, the radiation direction of the transmission beam transmitted from the wireless communication device is maintained to be a direction shifted to either the left or right from the direction in which the radio wave intensity shows a peak value, and the moving direction of the moving body is detected based on an increase or decrease in the radio wave intensity after the start of detection. A wireless communication device comprising:

2. 2. The wireless communication device according to claim 1, The control circuit The radio wave intensity of a transmission beam transmitted from the wireless communication device is changed, and the moving direction of the mobile object is detected based on the magnitude of the change in the radio wave intensity detected by the mobile object relative to the change in the radio wave intensity of the transmission beam. A wireless communication device comprising:

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